Until the 1960s, vehicles were lightweight and were not expected to be high-speed. The burden on tires was therefore low, and bias tires with a narrow section width were used. These days, however, as vehicles have increased in weight and speed, radial tires with a larger width have been adopted (for example, Patent Literature 1).
As compared to a bias tire, a tire with a radial carcass has a more rigid tire crown and thus has excellent resistance to uneven wear. Since the crown is rigid and propagation of movement between structural members of the tire is suppressed, rolling resistance is reduced. Therefore, tires with a radial carcass have good fuel efficiency and high cornering power.
The increased tire width also increases the contact patch area of the tire, thereby increasing the cornering power.
The increased tire width, however, reduces passenger comfort by compressing the vehicle space. Air resistance also increases, causing the problem of poor fuel efficiency.
In recent years, increased concerns for environmental issues have led to more stringent demands for fuel efficiency. In particular, in electric vehicles, which are becoming a practical vehicle for the future, it is necessary to guarantee space around the tire axle for storing drive components, such as a motor that controls torque for rotating the tire. The importance of guaranteeing space around tires is thus increasing.